/Engine/Source/Editor/BlueprintGraph/Classes/K2Node_CustomEvent.h
If a CustomEvent overrides another CustomEvent, then it inherits the super's net flags. This method does that work for you, either returning the super function's flags, or this node's flags (if it's not an override).
If this CustomEvent is an override, then this is the super's net flags, otherwise it's from the FunctionFlags set on this node.
uint32 GetNetFlags() const